1. Technical Field
The present invention relates to a plasma reactor for generating an active gas including ions, free radicals, atoms and molecules by plasma discharging and performing plasma processing of a solid, powder, gas or the like by using the active gas and, more particularly, to a multi-path inductively coupled plasma.
2. Discussion of Related Art
Plasma discharge is used for gas excitation to generate an active gas including ions, free radicals, atoms and molecules. An active gas is widely used in various fields. An active gas is generally used in semiconductor fabrication processes, for example, such as etching, deposition, cleaning, ashing and the like.
A wafer for fabricating a semiconductor device or an LCD glass substrate becomes lager. Accordingly, a plasma source needs to have high capability of controlling plasma ion energy and to have easy expandability with large-area processing capability.
Types of plasma sources for generating plasma are diverse. Typical examples of plasma sources using radio frequency include capacitively coupled plasma and inductively coupled plasma. It is known that the inductively coupled plasma is suitable for obtaining high-density plasma since it is capable of relatively easily increasing the ion density as radio frequency power increases.
However, in the type of inductively coupled plasma, a high-voltage driving coil is used because the energy binding with plasma is low compared with the energy as supplied. Consequently, since the ion energy is high, the inside surface of a plasma reactor may be damaged by ion bombardment. The damage to the inside surface of a plasma reactor by the ion bombardment not only shortens the life of the plasma reactor but also influences as a pollution source of plasma processing, resulting in a negative output. When decreasing the ion energy, since the energy binding with plasma is low, plasma discharging may be off. Therefore, in the inductively coupled plasma, it is difficult to stably keep plasma.
Meanwhile, remote plasma is very usefully applied in a process of using plasma in the semiconductor fabrication process. For example, the remote plasma is usefully used in a cleaning process of a process chamber or an ashing process for photoresist strip. However, since the volume of a process chamber increases as a substrate to be processed becomes larger, a plasma source needs to remotely supply a sufficient amount of high-density active gas.
To generate high-density plasma in a great quantity, the volume of a plasma reactor needs to increase. In most remote plasma reactors, the reactor is generally installed at an upper position of a process chamber. Then, when the size of the reactor increases, it is not easy to install the reactor. Moreover, in the plasma reactor having the structure in that a magnetic core forming a transformer is wound around the plasma chamber, called the toroidal structure, one or more insulating regions are included to interrupt an eddy current from generating in the plasma chamber. The plasma chamber having the aforementioned separate structure may have the problem of lowering the security and coherence in installing a large-volume plasma reactor. Moreover, when a radio frequency generator and a plasma reactor are constituted in a single unit like a conventional technique, it is more likely to have the aforementioned problem.